Download biochemistry/docs/Protein Structure 2

Protein Structure 2
Higher Order Protein Structures
Hierarchy of Protein Structure
Primary sequence- The amino acid sequence of a polypeptide, listed from
N-terminus to C-terminus.
Secondary structure- Recurring structural feature of proteins stabilized
exclusively by hydrogen bonds between peptide bond elements.
Supersecondary structure- Recurring structural feature of proteins
composed of two or more secondary structural elements.
Domain- A segment of protein structure that is autonomously stable.
Tertiary structure- A stable, independent protein encoded by a single gene.
Quaternary structure- A complex structure composed of two or more tertiary
structure subunits.
Alpha-fibrous proteins: Coiled-coil Helix
Supersecondary Structure
Heptad repeats in GCN4
Four-helical bundle
Sequence Comparison Reveals Positional Preference
Within Heptad Repeats
Max1 as an Example of a Leucine Zipper Motif Protein
Parallel and Anti-parallel Beta Sheets
anti-parallel
parallel
 Supersecondary Structures
Structure of -grasp fold of
ubiquitin showing  motif
Repeating  motifs (n=7) form a Rossmann fold structure
 Supersecondary Structures
Greek key motif
Beta meander motif
-coil- Supersecondary Structure
IpaH3.0
Domains and Tertiary Structure
Domains- Structurally autologous structures possessing discrete functions
that comprises part of the tertiary structure (beads on a string). Domains
can be identified by their characteristic sequences.
Ex: DNA binding domains, NAD+/NADP+ binding domains, HECT domains, Zn
finger domains, etc.
Motif- A highly conserved, short amino acid sequence that identifies a
discrete function.
Ex: Protein kinase phosphorylation motifs, Ca++ binding motifs, etc.
Pyruvate kinase domain structure
Quaternary Structure